"exchange theories"

I probably need to look for them better but in the meanwhile:

Personal headcanons about Caleb learning Undercommon for Essek:

Caleb starts using undercommon pet names for Essek next to the zemnian ones (this also connects to my idea that Caleb uses pet names way more frequently than Essek, but maybe sometimes Essek also replies with undercommon pet names :'D)

Thanks to his perfect memory Caleb learns all the grammar he can incredibly quickly, but that doesn't do shit against his terrible thick zemnian accent. Essek teases him about it even if he secretly finds it adorable.

I think it makes sense if the Dynasty has two different words for "first time spouse" and "spouse across multiple lifetimes" (considering their whole deal), and if your first time partner starts to switch it up and call you by the other term it's a Big Deal!!!! It means they will find you and love you in all of their lifetimes!!!! It's a commitment it's a promise!!!!

Except that in the "Undercommon for dummies" grammar book Caleb found there isn't the full context of the term. It just says that the [word for partners across multiple lifetimes] is occasionally used instead of [word for first time partners] to show your commitment to the person. So naturally Caleb goes "I want to use that one!! So Essek knows how much I care about him!!!"

Cue to Caleb calling Essek [word for partners across multiple lifetimes] and Essek turning around at the speed of light going "HUH???????????"

wet cat man! wet cat man! wet-

When two wizards combine their brilliant minds, the result is… an unexpectedly adorable cat tree.